The invention relates to improvements in coupling devices in general, and more particularly to improvements in so-called connectors which can be used to separably couple pairs of profiled structural members in the form of columns, beams, tubes, rods or the like.
It is often necessary to assemble two or more profiled members into a frame in such a way that the thus coupled members can be readily separated from each other, e.g., to collapse the frame for the purposes of transport, to replace a damaged member and/or for other reasons.
German Pat. No. 31 53 232 discloses a connector which can be used to separably couple profiled structural members to each other and which permits detachment of a selected profiled member from the other member or members. A drawback of the patented connector is that its reliability under certain circumstances is not entirely satisfactory. The connector employs a profiled plate with a single hook-shaped jaw or claw and relies on the so-called pushbutton principle to attach the connector to, or to detach the connector from, a profiled member. Since the connector employs a single jaw or claw, it can properly engage an internal surface only at one side of the locus of introduction of the single claw into an internal compartment of a profiled member which is to be separably coupled to the profiled member containing or supporting the patented connector. The plate which carries the single claw has an integral spring which bears against the housing of the connector to urge the plate and the claw in a given direction, namely to urge the plate against a cam which shifts the claw sideways during a certain stage of application of the patented connector. The spring acts close to the claw, i.e., at the front end of the plate. Therefore, the bias of such spring in a direction to maintain the eccentric (which can move the plate relative to its housing) in requisite position (namely to prevent detachment of the connector from the profiled member in which the connector is installed) is negligible. This affects the safety of the patented connector and of the assembly of profiled members which is obtained by resorting to one or more patented connectors. It has been found that, in certain instances, the eccentric is not likely to snap into the profiled member in which the patented connector is installed.
German Pat. No. 22 39 370 discloses a connector wherein two plates are installed in a common housing and can be moved relative to the housing in response to rotation of a single eccentric. The outer ends of the plates abut each other; nevertheless, the combined thickness of such plates, in addition to the combined thickness of claws and cams, is excessive for many applications where the claws of the connector should be capable of passing through relatively narrow slots or other inlets to internal compartments of certain profiled members. Moreover, this patent does not disclose or suggest to operate the eccentric as a pushbutton in order to drive the eccentric into the respective profiled member preparatory to removal of the patented connector from such profiled member. The reason is that the patented connector must employ two discrete biasing devices, one for each plate, and such biasing devices must act in opposite directions in order to bias the plates toward and against each other as well as against a post or stud between two inclined surfaces of the plates.
U.S. Pat. No. 4,799,819 to Swoboda discloses a connector wherein the free ends of legs of a substantially U-shaped coupling member are adjacent each other (they lie against each other face-to-face) and have claws which extend in opposite directions. The coupling member is reciprocable by an eccentric which also serves to displace a mobile cam between the legs of the U-shaped coupling member. The cam spreads the claws apart subsequent to introduction into the internal compartment of a profiled member so that the claws can engage the internal surface of the profiled member at opposite sides of an inlet to the internal compartment. The patentee further proposes a connector which can engage a T-shaped profiled member, again by utilizing one or more cams which are movable longitudinally of the housing for the profiled U-shaped coupling member.